The Cognitive Costs of Sleep Deprivation in Ultra-Endurance Cycling: Insights From the Race Across France.

For athletes in endurance sports, who compete over several days and in unpredictable conditions, managing sleep-wake rhythms is critical to ensure optimal performance and minimise the risks to safety. Despite its growing popularity, the role of sleep management on ultracycling performance has received little attention. We analysed the sleep strategies of ultracyclists to better understand (1) how sleep strategies and durations are related to race time and (2) how sleep debt and circadian timing are related to subjective sleepiness and cognitive performance. Twenty-three cyclists completed the study. To track cyclists' sleep, participants wore a wrist-worn accelerometer throughout a long-distance endurance cycling competition. From before the race start until the end, participants rated their sleepiness every 4 h. They also completed a cognitive task at basecamp on five occasions (before start, 620 km, 1438 km, 2066 km and after crossing the finish line). We observed that participants with higher mean sleep times per 24 h finished with higher race rankings. Perceived sleepiness was greater for those who slept less than 5.29 h per day on average, showing a distinct 24 h rhythm. In addition, cognitive performance was worse and response times were slower for those who slept less across days. The findings from this study demonstrate that sleep duration and timing are imperative for preserving physical and cognitive well-being during ultracycling races. Adopting sleep timing strategies, particularly ones that align sleep with homeostatic and circadian drives for sleep, may improve athletes' ultracycling performance.